Vehicle restraints are employed to lock a truck or other vehicle to a loading dock to prevent the truck from accidentally pulling away from the dock during a loading operation.
U.S. Pat. No. 4,695,216 describes a vehicle restraint having a mounting plate which is mounted on the front vertical surface of the dock and a slide is mounted for sliding movement on the mounting plate. To guide the slide in movement, the slide carries two sets of vertically spaced rollers which ride on guide tracks on the dock face. The forward end of the slide is inclined, sloping downwardly and outwardly from the dock and the slide is biased to an upper position.
With the vehicle restraint of U.S. Pat. No. 4,695,216, an ICC bar of a truck will engage the inclined surface of the slide, wedging or camming the slide down against the biasing means and the ICC bar will then engage a recess or notch formed in the upper surface of the slide. Engagement of the ICC bar with the notch will prevent the truck from pulling away from the dock during the loading operation.
In the construction of U.S. Pat. No. 4,695,216 the ICC bar is released from the notch through use of a release bar that is mounted for movement relative to the slide. The release bar is moved upwardly against the ICC bar, thereby resulting in a downward force being applied to the slide which will move the slide downwardly against the force of the biasing means to release the ICC bar from engagement with the notch, thus enabling the truck to pull away from the dock.
The vehicle restraint of U.S. Pat. No. 4,695,216 also can incorporate an extension leg which is pivotally connected to the slide and forms an extension to the inclined surface of the slide. The leg is prevented from pivoting downwardly relative to the slide but can freely pivot upward. If a truck having a low ICC bar backs toward the dock, the ICC bar will initially engage the extension leg wedging the slide downwardly and the ICC bar will then ride upwardly along the inclined surface of the slide. As the ICC bar rides against the inclined slide, the extension leg will be pivoted upwardly through the connection of a fixed link to the frame, thereby enabling the slide to continue to move downwardly until the ICC bar engages the notch in the upper edge of the slide. The use of the extension leg increases the operating range of the vehicle restraint for a slide of given vertical dimension.
In the typical truck actuated vehicle restraint in which the truck ICC bar engages a slide or carriage and wedges the slide downwardly, there is a substantial force exerted by the truck through the slide to the guide rollers. Because of the force, the guide rollers and bearings must be constructed of heavy stock and the two sets of guide rollers must be spaced a substantial distance apart. The increased spacing between the sets of rollers increases the vertical depth of the slide and thus reduces its operational range.